Garbage and waste are produced in communities in great quantities. This garbage and waste must be disposed of in a variety of ways. The disposal of various kinds of garbage and waste in large quantities in cities is one of the important new administrative problems facing city government. Typical methods for the disposal of garbage include discharging garbage into the sea for reclamation and burying garbage underground. However, there are great problems, such as pollution of sea water and difficulty in getting land, associated with these methods. The general trend at present is directed toward the disposal of garbage by complete incineration. However, and unfortunately, the prevailing technique for the disposal of garbage is by incineration, a method used which burns garbage on fire grates with large quantities of air supplied, thus creating a number of associated problems.
It has been found that the use of large quantities of air produces large quantities of exhaust gases, thereby creating and exacerbating air pollution. Since the combustion temperature of garbage is relatively low, the residue of burnt garbage cannot be made completely harmless. A great deal of environmental pollution is caused by such effluents from this incineration process. Since the combustion of garbage on fire grates is unstable, the efficiency of heat recovery is low and it is difficult to effectively use the heat generated by the combustion and garbage. Additionally, vast space is occupied by the fire grates. This requires a large area for the combustion site. Furthermore, there is a difficulty in getting the sites for the construction of large incinerating plants because of the environmental problems associated therewith.
Recently, disposal methods have been proposed which attempt to solve some of the problems associated with thermal decomposition. Essentially, the garbage is introduced into an incinerator with the heat necessary for thermal decomposition so as to produce a generated slag and gas. There are two processes that are available--a process which uses external heat as an intense heat source necessary for thermal decomposition and a process which utilizes heat generated by the partial oxidation of the garbage with air or oxygen supplied. In the former process, since an external heat is used, the problem lies in economy. In the latter process, since combustion gas gets mixed with generated gas, the calorific value of generated gas is decreased, disadvantageously making the usefulness of the generated gas inferior to that of the former process.
Another problem facing city governments is the disposal of toxic or hazardous materials, such as polychlorinated biphenyls (PCB's) These are toxic and hazardous compounds whose use is being withdrawn or prohibited because of the irreversible harm to the health and the environment. These materials must be managed and disposed of effectively. In addition to polychlorinated biphenyls, there are also organophosphorous, organonitrogen, and organometallic compounds, as well as other materials, that exist in massive quantities and demand effective means of disposal. The majority of the toxic compounds are in a complex matrix format often combining organic and inorganic compounds or fractions, and in these cases, little or no disposal technology is available.
Various methods have been used for disposing of these toxic wastes, including thermal destruction, chemical detoxification, long-term encapsulation and specific landfill methods. With the exception of high temperature incineration, little success has been demonstrated for the safe disposal of highly toxic or extremely persistent waste, such as PCB's. The methods that have been tried have either not been able to handle anything but homogenous waste feed streams or they have only been able to handle relatively low concentrations of toxic compounds in the waste materials. Further, very few of the disposal methods tried to date have been able to develop to operate on a commercial scale.
Of the many methods tried for the disposal of toxic or hazardous wastes, thermal destruction has been the most promising. However, the toxic waste materials are usually very stable organic molecules, and they require long dwell times at high temperatures to effect thermal destruction. Some combustion or incineration systems can achieve the necessary conditions, but the facilities required are very large scale, and often the products of the combustion process present as much of a disposal problem as the original toxic wastes.
In the past, attempts have been made to use electric plasma arcs to destroy toxic wastes. An electric plasma arc system, being essentially pyrolytic, overcomes many of the deficiencies of an incineration or combustion process. The volume of gaseous products produced is much less. As a result, the equipment is substantially smaller in scale. Laboratory demonstrations have shown that a plasma ar is capable of atomizing and ionizing toxic organic compounds, and these atoms and ions usually recombine into simple products. While residual toxic materials are formed, these can be captured, so that no significant amount of toxic material is released to the environment.
Unfortunately, such pyrolytic destruction of waste materials is not suitable for a commercially viable system. Often, the gaseous products that are released into the environment can contribute to various forms of air pollution. In addition, the release of such gases causes concern among the various regulatory authorities in control of the destruction of such toxic materials. Furthermore, and importantly, such plasma arc, pyrolytic methods of waste destruction are extremely costly processes. The cost of the power needed to operate lasers, plasma arcs, or various other methods, cannot be justified on a large scale garbage disposal basis. Furthermore, the by-products of the combustion process are not acquired for later sale or cost offset.
Various United States patents have attempted to address the issue of waste disposal by high temperature incineration process. U.S. Pat. No. 4,665,841, issued on May 19, 1987, describes a municipal trash destruction system in which hydraulic systems move the rubbish, garbage, and other municipal trash into a processor. The processor includes a trash processing zone, a fractionating system, a combustion zone, a heating exchange zone, a waste heat recovery system, and a precipitator for cleaning the emissions prior to release into the atmosphere. U.S. Pat. No. 4,644,877, issued on Feb. 24, 1987, describes the pyrolytic destruction of toxic and hazardous waste materials. The waste materials are fed into a plasma arc burner where they are atomized and ionized. These materials are then discharged into a reaction chamber to be cooled and recombined into product gas and particulate matter. The product gas is then extracted from the recombining products using a scrubber. The product gas may then be burned and utilized as a fuel. U.S. Pat. No. 4,695,448, issued on Sept. 22, 1987, describes the dissociating of toxic compounds by an electric arc (e.g. 12,000.degree. F.) in an airtight chamber charged with oxygen. U.S. Pat. No. 4,759,300, issued on July 26, 1988, shows a method and apparatus for the pyrolysis of waste products. In this invention, the waste materials to be pyrolyzed are efficiently dehydrated prior to introduction into the pyrolysis retort using microwaves generated by a large microwave generator. After the waste material is dried, the initial ignition of the material is accomplished by using a high intensity laser beam. Laser ignition is continued until sufficient methane and other volatile gases are produced for burning in a burner unit to sustain the pyrolysis reaction. U.S. Pat. No. 4,667,609, issued on May 26, 1987, describes the destruction of soil contaminated with hydrocarbons by passing the material through a sealed, negatively pressurized, high temperature furnace. The temperature in one zone of this process is maintained at 2,900.degree. F. so as to effectively destroy the contaminating hydrocarbons. U.S. Patent No. 3,575,119 shows an apparatus for disintegrating and incinerating a concentrated slurry of solid organic material. Material passes through an arcuate tunnel having a plurality of arc electrodes spaced therealong. These electrodes cause the temperature to abruptly raise from about 2,000.degree. F. to about 15,000.degree. F. so as to dissolve the bonds between the carbon and the other atoms.
In the past, various techniques have been used to create high temperature burning systems. Typically, these rely on vast quantities of fuel. It has been found that the expense of attaining such destruction of waste could not justify the technique for the destruction of waste. Whenever vast quantities of fuel are required to attain a desired temperature, the cost of such fuel becomes an important consideration when evaluating the merits of a waste disposal system. As such, it was difficult to justify the benefits of the pyrolysis of waste since the cost of such waste destruction is so expensive.
Various U.S. patents have attempted to create large temperatures by the dissociation of water. For example, U.S. Pat. No. 4,848,250, issued on July 18, 1989 to J. M. Wunderley, describes a refuse container in which refuse is injected into an ignition chamber so as to ignite a readily burnable material. Water in the refuse reacts with the carbon to produce a hydrogen gas. The gas is passed to a secondary chamber wherein the hydrogen is burnt, resulting in an increase in temperature to above 3,000.degree. F. and producing water. Because of this high temperature, the water dissociates into hydrogen and oxygen. The hydrogen burns repeatedly and forms water and hydrogen in rapid succession, thereby generating thermal energy devoid of particulate matter. At high temperatures, water is dissociated into its hydrogen and oxygen components. This spontaneous occurrence keeps the system operating at temperatures of above 3000.degree. F. This does not use the combination of oxygen and hydrocarbons.
U.S. Pat. No. 4,132,065, issued on Jan. 2, 1979 to R. McGann describes a system in which a free-oxygen containing gas is heated while under pressure in a gas-fired pressurized heater and then reacted with a hydrocarbonaceous fuel. The system is designed to produce a H.sub.2 +CO-containing product gas. One portion of the product gas is reacted in the pressurized heater with air in order to heat the free-oxygen containing gas going into the gas generator.
U.S. Pat. No. 4,242,076, issued on Dec. 30, 1980, to E. Rawyler-Ehrat, describes a process of combustion in which the dissociation of water vapor is promoted by the presence of a catalyst. This catalyst is a glowing carbon. The presence of active oxygen is sufficient to activate the combustion process. A nozzle is used for the introduction of water vapor into the combustion chamber of the process.
It is an object of the present invention to provide a waste disposal system that cleanly burns the waste material.
It is another object of the present invention to provide a waste disposal system that is inexpensive and economically beneficial.
It is a further object of the present invention to provide a waste disposal system in which waste-destroying temperatures are achieved by the dissociation of water.
It is still another object of the present invention to provide a waste disposal system in which waste hydrocarbons can be used for the purpose of attaining high waste-destroying temperatures.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.